I agree with the other answerers. This business is ready to fold, and they are desperate for cash. They do not want to, or do not have the cash, to pay the payroll taxes. They are withholding your retirement money and not investing it.
Get another job immediately. Until you do, keep records of your hours worked and payments received. Contact the Department of Labor for your state. Your employer has misclassified you. You will not have to pay the employer's SS and medicare, only your part. Your employer is required to participate in worker's comp and the state unemployment insurance on your behalf.
As for your retirement money, you can get a copy of the plan from the plan administrator. If your employer is keeping your money and not depositing it, I would call the US Department of Labor hotline 866-444-3272.
I would be worried that this employer may in fact be taking money out of your retirement accounts, check with your plan administrator and raise hell if you see this happening (DOL hotline number above).